<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var arr = Object.create(null)
    arr.width = 400;
    arr.height = 200;
    arr.position = "relative";
    arr.background = "#eeefff";

    Object.assign(arr, { border: '1px solid red' });


    console.log(arr)
</script>
</body>
</html>